Many present day electronic designs, especially those found in radios, offer different methods of shielding and attenuating circuitry from harmful radio frequency interference. Radio frequency signals can cause severe problems in different types of circuits especially those found in modern day radios. One of the most common methods of attenuating undesired radio frequency interference in electronic circuits is by designing the electronic circuit in a modular format, with most of the sensitive sections designed in their own shielded electronic modules. An example of this would be the circuits found in radios (i.e. the voltage controlled oscillator section, synthesizer, etc.) where each section of the radio is designed and placed in its shielded module. Other methods to shield circuitry from radio frequency interference that are employed in the art include: the use of filters such as ceramic feedthrough filters, multilayered chip capacitors, employing ground planes in multilayer circuit boards wherever possible to minimize radio frequency (RF) interference, and use of shielded housings around RF critical circuitry.
The above mentioned methods for attenuating radio interference from electronic circuitry are fairly effective. The major problem with the above mentioned methods are that they normally require additional electronic parts to implement; as in the case of the use of conventional ceramic feedthrough filters, or multilayer chip capacitors. In the case of the shielded module design, radio frequency signals can sometimes still interfere with low frequency input signal lines going into the module (i.e. VCO input line). Any undesired radio frequency interference signal that gets coupled onto an input/output line connected to a module reduces the effectiveness of the shielding of the modular structure, and thus reduces the performance of the particular circuit. Therefore, there is a need in the art for a way of further shielding sensitive multilayer electronic circuitry from harmful radio frequency signals, without having to use extra electronic components.